Brazil great Pele, regarded by many as the best to ever play the game, scored 643 times in just 656 matches for Santos between 1956 and 1974.
While Pele's overall goals record for his entire career is disputed, he did net 643 goals in official competition for Santos.
Some believed Pele's haul to be a world record in top-level football, though statisticians are unable to confirm this with absolute certainty.
Nevertheless, this is unlikely to detract from Messi's accomplishment, as he drew level with Pele's remarkable total after scoring with a header in first-half stoppage time on Saturday.
Having initially seen a penalty saved by Jaume Domenech, Messi got his milestone goal when he met a cross from the left and nodded home from point-blank range.
Remarkably, his latest goal was also his 450th in LaLiga, making him the first player to reach that figure for a single club in any of Europe's top five leagues.
Messi has attracted criticism this term as his performances have not been at the level many might have expected them to be.
But his latest goal took him on to six from 13 LaLiga matches in the 2020-21 campaign.
The 33-year-old scored his first Barca goal on May 1, 2005 against Albacete in LaLiga when he was 17, at the time becoming the club's youngest ever goalscorer.
He has since gone on to become Barca's all-time leading scorer, as well as LaLiga's, and has won the Ballon d'Or a record six times.
But how much longer he will remain at Camp Nou remains a topic of much debate.
Messi attempted to force a transfer away from the Blaugrana in pre-season, adamant a get-out clause in his contract provided him with the opportunity to leave on a free transfer.
But then-president Josep Maria Bartomeu stood in his way, Messi ultimately backing down as he was unwilling to drag Barca through the courts.
Recently, Paris Saint-Germain have emerged as possible favorites to sign Messi, with Neymar having expressed a desire to play alongside his former Barca team-mate in 2021.